In presently-used devices which meter an amount of fluid, leak-resistant seals are difficult to form. Typically, as shown in FIG. 1, devices of this type include an orifice seal member 10 and an orifice housing 12. The housing 12 provides a central bore 14 which sealably receives a fluid carrying conduit (not shown) and threadably receives the orifice seal member 10. The orifice seal member provides a fluid passage 16 which communicates fluid from the central bore 14 to a metering orifice 18.
The central bore 14 is sealed by engaging a surface 20 surrounding the central bore, which defines a seat, with an annular surface 22 provided by the orifice seal member 10. Although this arrangement works satisfactorily some of the time, there exists a reoccurring problem in forming a reliable seal between the seat 20 and the annular surface 22 and, therefore, leaks develop.
Surface imperfections in the seat 20, either created at the time of manufacturing the orifice housing 12 or at a later time, allow fluid to leak out of the central bore 14. Since the orifice seal member 10 is designed to be replaced or exchanged for other seal members which provide a different metered flow, the seat 20, in its location at the top surface of the orifice housing 12, is susceptible to damaging contact each time the orifice seal member 10 is removed. Also, the seat, due to its being part of a much larger surface, is generally not compressible and, therefore, generally intolerant, from a sealing standpoint, of surface imperfections. In devices of the aforementioned type, when surface imperfections are present in the seat 20, fluid from within the central bore 14 leaks out between the seat 20 and the annular surface 22.
In attempting to stop the leaks, the installer will typically over-tighten the orifice seal member 10, causing its head portion 24 to deform or bulge. If over-tightened to much, the head portion 24 will be so misshapen that the normal compression tests cannot be performed. Even when over-tightened to this extent leaks persist due, in part, to the incompressibility of the seat 20.
Therefore, there exists a need in the art for a device which provides a reliable seal between the orifice seal member and the orifice housing. There also exists a need for an orifice housing which provides a protected sealing surface to reduce the chance that damaging contact with the sealing surface or seat provided by the orifice housing will occur. There also exists a need in the art for a device which provides a seal between the orifice seal member and the orifice housing that is tolerant of surface defects or imperfections.